The structure, organization, expression and evolution of IRBP (Interphotoreceptor retinol binding protein) gene(s) and mRNA(s) are being investigated. cDNA clones for IRBP are being constructed and identified. Two different cDNA libraries have been obtained. One library is an expression library in the Lambdagt11 vector system and is being screened with antibodies against IRPB. Several prospective positive clones have been obtained from the primary screening of this library, these clones are being re-examined to eliminate false-positives. A second library has been obtained that can be screened with oligonucleotide probes, the sequence of which is based on the known amino acid sequence of the N-terminus of IRBP.